Police Chief Usman Akran Gondal of Muzaffargarh district says the woman died Friday after setting herself on fire Thursday in the village of Beit Mir Hazar Khan.
Gondal says the woman's brother filed a complaint with police in January, saying his sister had been abducted and the assailants tried to rape her.
Gondal says authorities investigated the claim but found no evidence to support it so they let the men go.
The Human Rights Commission of Pakistan said the woman had gone to the police station to protest.
Rape cases are rarely prosecuted in Pakistan. Women who complain are often stigmatized. AP